This invention relates generally to transducer positioning apparatus and, more particularly, to improvements in apparatus for positioning a transducer head in a prescribed relationship relative to a selected track on a recording medium such as a magnetic tape.
A related application for U.S. Pat. Ser. No. 052,738, filed in the name of A. Bejerano et al and entitled "Optical Control System for Transducer Positioning Apparatus" is directed to an optical control system for use with transducer positioning apparatus of the present invention.
An example of a transducer positioning apparatus of this particular type is disclosed in U.S. Pat. No. 4,144,549, issued in the name of D. L. Burdorf et al and entitled "Transducer Positioning Device". As described in that patent, such apparatus includes a frame having a guide to direct the tape past the transducer head, and a cam mounted for rotation on the frame and having a graduated series of planar steps formed in its upper surface. The transducer head is carried by a platform assembly having a bearing post that is maintained in continuous contact with the steps of the cam, whereby controlled rotation of the cam causes the head to move upwardly or downwardly to prescribed positions corresponding to the positions of recording tracks on the magnetic tape.
One drawback to the aforedescribed prior art device arises when it is adapted for use with a recording tape having a relatively large number of tracks arranged in a very closely-spaced relationship. In such situations the cam must be formed with extreme accuracy and precision, so as a consequence, the manufacturing costs associated with this apparatus are relatively high. Additionally, since each of the graduated, planar steps of the rotatable cam corresponds to a separate track on the tape, the steps must be made exceedingly small. For example, when recording tapes having 72 tracks are used, each step of the cam can subtend, at most, only 5 degrees of arc. As a consequence, it can sometimes be difficult to index the transducer head by a prescribed number of tracks, without experiencing an overshoot onto the next successive track.
Another transducer positioning apparatus of this particular type is disclosed in U.S. Pat. No. 4,041,539, issued in the name of W. A. Robarge and entitled "Tape Head Shift Apparatus for Multi-Track Tape Player". The apparatus disclosed in that patent includes a rotatable cylindrical cam that is indexed by a geneva mechanism, in combination with a rather elaborate gearing mechanism. Although the apparatus is likely effective in incrementing the cam through a precise angle, it is nevertheless subject to high manufacturing costs, especially when adapted for use with a recording tape having a relatively large number of closely-spaced tracks.
It will be appreciated from the foregoing that there is still a need for apparatus that can accurately position a transducer head in a prescribed relationship relative to a selected track on a recording medium, without involving undue manufacturing costs, and without involving the possibility of overshooting the selected track when indexing the transducer head from one track to another. The present invention fulfills this need.